Antiplatelet drug which inhibits cyelo-oxygenase 1 enzyme is-

Ans. is 'a' i.eM Aspirin Pathophysiological pharmacology of antiplatelet drugso Platelate mechanismy cAMP plays a key role in platelet mechanism - antiaggregatory or aggregatory,High concentration of cAMP inhibit platelet adhesion, aggregation and the release of active substances.Low concentration of cAMP has an opposite effect.cAMP is formed by the action of enzyme adenylate cyclase and degraded by phosphodiesterase.Thromboxane A2. (synthesized in platelets) and ADP inhibit adenylate cyclase -- | cAMP - Platelet aggregation and adhesion.Prostacyclin PGI2 (Synthesized in endothelium) stimulates adenylate cyclase -| cAMP - antiaggregatory effectProstacyclin and thromboxane A2 are synthesized from prostaglandins that are formed from arachidonic acid by the action of cycloxygenase.o Platelet activationy Circulating resting platelets do not stick to healthy endothelium or each other.When there is damage to endothelium, constituents of the subendothelial matrix are exposed especially collagen and von wiilebrand factor.Platelets attach to these matrix constituents and there is simultaneous release of thromboxane - A2 (TXA2) and adenosine diphosphate.TXA2 and ADP are proaggregatory and vasoconstrictor mediators - they promote recruitment of additional platelets.These platelets bind to adhesive proteins like fibrinogen or fibrin and von wiilebrand factor through surface integrin glycoprotein GP IIa/IIIb - formation of platelet plug.o Anti platelet drugsAntiplatelet drugs act by inhibiting one or other proaggregative mediators or mechanism.Aspirin (in low doses) - inhibits synthesis of TXA, by inhibiting the enzyme cycloxygenase So that immediate precursor (prostaglandins) of TXA, are not synthesized.Ticlopidine, clopidogrel - they block ADP mediated cAMP inactivation.Dipyridamoi - Inhibits phosphodiesterase - T cAMP, It also blocks uptake of adenosine.Epoprostinol - A prostacyclin - | cAMP.Abciximaby eptifibatide, tirofiban - GPIIb. Ilia inhibitors.